Respuesta :

Answer:

1.In the first query the column Z of table xyz wil change and set to its  default value so we use alter command .

Syntax :ALTER TABLE TABLENAME  ALTER COLUMN NAME  SET DEFAULT VALUE

So SQL query is :

ALTER TABLE  XYZ  ALTER Z SET DEFAULT  9999  ;

This query will Change the column Z of a table XYZ to acceptdefault value 9999 .

2.In the second query we delete a table from database so we use DROP    command .

Syntax :DROP TABLE TABLENAME;

So SQL query is :DROP TABLE XYZ;

This query will delete the table from database.

3.In the last query we have to change the column Z from table again we      use alter command .

Syntax:ALTER TABLE TABLENAME  DROP  COLUMN  COLUMNNAME  ;

So SQL query is :

ALTER TABLE XYZ DROP COLUMN Z;

This query will delete column Z from the table XYZ.

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